1. Field of the Invention
The present invention generally relates to a method and apparatus for measuring weight, more particularly, a method and apparatus for measuring the weight of a CNC (Computer Numerical Control) workpiece.
2. Description of the Prior Art
A Computer Numerical Control (CNC) machine tool is used to shape a workpiece by removing a certain amount of unwanted material from the workpiece, thus reducing the weight of the workpiece and changing its inertia. As shown in FIG. 1, when certain amount is removed from a workpiece 105 by a conventional CNC machine tool 100, the workpiece is required to be unloaded from the loading platform and weighed by a weighing scale. The weight information is then entered into the CNC machine tool, so as to adjust relevant control parameters such that the machined contour conforms to a predicted contour 110, thereby obtaining optimal accuracy of the servo control. However, since there are a variety of machining applications and dynamic conditions (e.g. change of loading), it is difficult to obtain an optimal servo-control result for various kinds of machining applications with only a single set of fixed control parameters. As a result, for example as shown in FIG. 1, an error may occur between the actual contour 115 created and the predicted contour 110. Therefore, there is a need for a method and apparatus that can detect the weight of the workpiece in real time during CNC machining process that enhances the performance and accuracy of the CNC machine tool, thereby, for example, the surface precision of the workpiece is increased and the operating time and tracking error are reduced.